A. Field of Invention
This invention pertains to a fiber optic sensor for monitoring strain at several locations independently and more particularly to an optical sensor making use of Fabry-Perot cavities.
B. Description of the Prior Art
In many plants making use of heavy duty equipment, such as for example power utility plants, it is desirable to monitor the status of various rotary and stationary equipment. For example many utility companies are concerned about possible structural and component damages that can lead to catastrophic failure of systems. Thus, the need for real time automatic status monitoring technology in the power plant environment has been growing very rapidly. The ability to sense incipient failures reliably and plan corrective measures in advance can be very cost effective and can reduce or even eliminate power outages. However, currently available sensors are not suited for many of the applications because of the electromagnetic or thermal environments present. In the recent years fiber optic sensors have opened up applications for the sensing of many physical parameters because they possess a variety of advantages over their conventional counterparts. These advantages include a dielectric construction that permits usage in high voltage, electrically noisy, high temperature, corrosive or other hostile environments; geometric versatility that allows arbitrary configurations; and inherent compatibility with fiber optic data links. For example, these characteristics make fiber optic sensors an attractive way to monitor the status of stator end windings and phase connections in large generators by measuring the static and dynamic strain at key locations. Similarly, such fiber optic strain sensors offer advantages for monitoring the status of piping, headers, pressure vessels, boiler tubes, and turbine valves. Thus, the availability of a remote fiber optic strain sensor that can provide information regarding the condition of key structural components may be very beneficial to the utility industry. However even the present optic fiber sensors are difficult to utilize because an individual fiber is required for each sensor, leading to extensive fiber optic connections, elaborate interfaces between the sensors and the data interpreting location and complex data multiplexing schemes.